iOS知识小集-170508

Carthage

安装：brew install carthage
添加：Cartfile
运行：carthage update
添加：Carthage/Build/.framework

防止重复push/present类型相同的controller

找到最上层view controller；
判断最上层view controller与待展示view controller是否类型相同；
如果类型不同，才进行操作。获取最底层view controller：[UIApplication sharedApplication].delegate.window.rootViewController。
获取最上层view controller：

+ (UIViewController *)topViewController {
  return [self
      topViewControllerWithRootViewController:[UIApplication sharedApplication].delegate.window.rootViewController];
}

+ (UIViewController *)topViewControllerWithRootViewController:(UIViewController *)rootViewController {
  NSLog(@"root to top vc:%@", NSStringFromClass([rootViewController class]));
  if ([rootViewController isKindOfClass:[MMDrawerController class]]) {
    MMDrawerController *mmdVc = (MMDrawerController *)rootViewController;
    return [self topViewControllerWithRootViewController:mmdVc.centerViewController];
  } else if ([rootViewController isKindOfClass:[UITabBarController class]]) {
    UITabBarController *tabBarController = (UITabBarController *)rootViewController;
    return [self topViewControllerWithRootViewController:tabBarController.selectedViewController];
  } else if ([rootViewController isKindOfClass:[UINavigationController class]]) {
    UINavigationController *navigationController = (UINavigationController *)rootViewController;
    return [self topViewControllerWithRootViewController:navigationController.visibleViewController];
  } else if (rootViewController.presentedViewController) {
    UIViewController *presentedViewController = rootViewController.presentedViewController;
    return [self topViewControllerWithRootViewController:presentedViewController];
  } else {
    return rootViewController;
  }
}

Create Groups vs Create Folder References

Group：不创建文件夹，不能同名；
Folder：创建文件夹，可以重名；

拉伸Image

代码：- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets resizingMode:(UIImageResizingMode)resizingMode NS_AVAILABLE_IOS(6_0);
设置：Assets -> Attributes Inspector -> Slicing

隐藏文件

显示隐藏文件：defaults write com.apple.finder AppleShowAllFiles -bool true
隐藏隐藏文件：defaults write com.apple.finder AppleShowAllFiles -bool false 重启finder：killall Finder

NavigationBar & ScrollView

自动：contentOffset.y == -64
手动：self.edgesForExtendedLayout = UIRectEdgeNone;，y轴0点下移64。

Objective-C static vs external

static: In C and Objective-C, a static variable or function at global scope means that that symbol has internal linkage.
external: If you want to have a single global variable, you can’t have it in class scope like in C++. One option is to create a global variable with external linkage: declare the variable with the extern keyword in a header file, and then in one source file, define it at global scope without the extern keyword.

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